The present invention relates to a coating for metal shelving, particularly to a plastic coating suitable for plated metal shelving for use in walk-in coolers. The invention also relates to a method of applying the coating to the metal shelving and to the coated or finished article itself.
The use of metal shelving generally, and wire shelving specifically in walk-in coolers is well known. Because of the extremely corrosive environment in these walk-in coolers, owners have traditionally found it necessary to choose between costly stainless steel shelving which will resist corrosion and more economical plated carbon steel which has a limited life in such an environment.
A recent development in coatings for metals has been the introduction of plastic powder coatings which are of many types and which are generally applied over unplated metal parts. Some manufacturers of shelving for walk-in coolers have introduced shelving where the plastic coating is applied directly over a zinc-plated substrate.
It must be understood that in actual use in walk-in coolers, shelving is subjected to considerable mechanical abuse; and virtually any coating will begin to chip after a period of time. When this happens, these zinc-epoxy systems are deemed to be deficient in two areas. First, because the plastic coating is opaque, the area where coating has chipped off can be readily seen and gives an objectionable appearance. Secondly, the zinc coating, being sacrificial to steel, begins to oxidize under the coating. As a result, the coating looses adhesion and lifts off in increasing amounts.